“Active tip clearance” refers to a gas turbine engine system whereby the radial gap between the turbine blades and surrounding static shroud is varied during the engine cycle in order to optimize tip clearance. Active tip clearance control (ATCC) usually uses compressor or bypass air to selectively cool the turbine shrouds to affect tip clearance. The use of bypass air is preferred because it is less thermodynamically “expensive” for the engine (i.e. more efficient). However, bypass air which is driven by a fan assembly is at a much lower pressure than air bled from the compressor assembly (e.g. P3 air) of the gas turbine engine. For a gas turbine engine application with a short duct nacelle, prior art utilizes a port on the side of the fan air stream bypass duct, to tap off air and deliver same through a pipe and a valve to its ultimate end use as turbine cooling air, after which it vents to the atmosphere. The valve is usually a butterfly style and has relatively high pressure losses. Therefore, long duct nacelle engines with a low pressure differential in the bypass air are challenged in using bypass air in an ATCC system because the sink pressure is higher than that of the atmosphere.
Accordingly, there is a need to provide an improved arrangement.